Self-Supporting Triphase Photocatalytic CO₂ Reduction to CH₃OH on Controllable Core–Shell Structure with Tunable Interfacial Wettability

Enhancing the CO₂ mass transfer and proton supply in the photocatalytic reduction of CO₂ with H₂O into CH₃OH (PRC-M), while avoiding the hydrogen evolution reaction (HER), remains a challenge. Herein, we propose an approach to control the surface coverage of CO₂ and H₂O by modifying interfacial wettability, which is achieved by modulating the core–shell structure to expose either hydrophobic melamine-resorcinol-formaldehyde (MRF) or hydrophilic NiAl-layered double hydroxides (NAL). Characterizations reveal that an insufficient proton supply leads to the production of competing CO, while excessive coverage of H₂O results in undesired HER. The NAL-MRF integrates hydrophobic and hydrophilic interfaces, contributing to the CO₂ mass transfer and H₂O adsorption, respectively. This combination forms a microreactor that facilitates the triphase photocatalysis of CO₂, H₂O, and catalyst, allowing for high local concentrations of both *CO and *H without competing binding sites. Importantly, the formation of covalent bonds and a Z-type heterojunction between hydrophilic NAL and hydrophobic MRF layers accelerates the charge separation. Furthermore, the density functional theory results indicate that the NAL linking promotes the continuous hydrogenation of *CO. As a result, an enhanced CH₃OH yield of 31.41 μmol g^–1 h^–1, with selectivity of 93.62%, is achieved without hole scavengers or precious metals.